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K Amann

Publications and source records attributed to K Amann.

108 records · Page 6Linked to original sources
PubMed1993

Increased resistance against shortening in myocardium from recipient hearts of 7 patients transplanted for dilated cardiomyopathy.

UNLABELLED: The contractile behaviour of demembranized atrial and ventricular myocardium of 7 patients transplanted for end-stage heart failure (ESHF) was analyzed. Atrial muscle specimens of patients undergoing coronary artery bypass surgery (n = 9) and pig papillary muscle were used as reference preparations (n = 9). Extreme care was taken for dissection and mounting the muscle fibres (0.3 x 6 mm) in order to keep the passive series compliance small. Calcium sensitivity, cross-bridge cycling rate (estimated by the force-clamping technique and calculation of the shortening velocity at zero load [Vmax]) and isometric force development were measured. Analysis on light- and electronmicroscopic level was carried out. RESULTS: 1) Calcium sensitivity was not altered in ESHF patients; 2) the velocity of the force generating process (cross-bridge cycling rate) was normal in ventricular and reduced in atrial ESHF myocardium, 3) maximum isometric force development was reduced in ventricular, but not in atrial myocardium of ESHF patients, and 4) Vmax was significantly reduced in ventricular and atrial ESHF myocardium (p < 0.0001). Perimysial and endomysial fibrosis was present in ventricular, not in atrial myocardium of ESHF patients. CONCLUSION: A normal cross-bridge cycling rate in left-ventricular ESHF myocardium combined with a decreased capability of muscle shortening indicates the presence of a resistance against shortening localized either on the cross-bridge level or/and due to intra- and pericellular fibrosis. Left-ventricular contractile dysfunction in patients with end-stage heart failure may be related to a normal contractile apparatus contracting within an abnormal intracellular or interstitial environment.

Animals↗
PubMed1993

The effect of enalapril on glomerular growth and glomerular lesions after subtotal nephrectomy in the rat: a stereological analysis.

INTRODUCTION: Angiotensin converting enzyme (ACE) inhibitors have a beneficial effect on glomerular injury in different models of renal damage. Their presumed nephroprotective action has been related partly to actions on glomerular growth. We examined the effect of prophylactic administration of a moderate dose of enalapril (50 mg/l in drinking water) in male Sprague-Dawley rats on a diet containing 40% protein and moderate NaCl. METHODS: The rats were followed for 8 weeks after subtotal nephrectomy and compared with sham-operated matched controls. RESULTS: The number of glomeruli per kidney was reduced significantly in both the enalapril-treated and control groups. The median glomerulosclerosis index was significantly lower in the enalapril-treated than in the untreated subtotally nephrectomized rats. The mean absolute glomerular volume was significantly higher after subtotal nephrectomy, but was significantly lower in the enalapril-treated than in the untreated subtotally nephrectomized rats. The total numbers of cells per glomerulus and of mesangial or endothelial cells, as well as nuclear volumes of mesangial cells and the total capillary length per glomerulus, were all significantly higher after subtotal nephrectomy. These parameters were significantly lower in the enalapril-treated than in the untreated nephrectomized rats. The rise in systemic blood pressure was modest in the nephrectomized rats and the arteriolar volume: length ratio was unchanged by treatment with enalapril. CONCLUSIONS: In subtotally nephrectomized rats enalapril inhibits (but fails to reverse completely) the compensatory glomerular enlargement and the increase in mesangial cell number and activation, with a concomitant reduction in the development of glomerulosclerosis. The results is compatible with antiproliferative, and possibly antiangiogenic, actions of ACE inhibitors.

Animals↗
PubMed1993

Structural causes of cardiac dysfunction in uremia.

While coronary heart disease is undoubtedly a major cause of cardiac morbidity and mortality in uremia, important noncoronary problems contribute to the common presence of cardiac problems. Based on clinical and experimental studies, we could show: (i) Left ventricular hypertrophy (LVH) can be dissociated, at least in part, from elevation of blood pressure. (ii) In uremia, PTH-dependent intermyocardiocytic fibrosis occurs; it may account, at least in part, for disturbed LV compliance and contribute to the arrhythmogenic potential. (iii) Blood pressure-independent abnormalities of intracardiac arterioles and reduced myocardial capillary supply are observed.

Animals↗
PubMed1992

Effects of combined renovascular hypertension and diabetes mellitus on myocardial cells, non-vascular interstitium and capillaries: a stereological study on rat hearts.

The effects of combined renovascular hypertension and diabetes mellitus on the rat heart were investigated in order to detect possible synergistic effects of the two conditions. Hypertensive diabetic and hypertensive non-diabetic animals were compared to diabetic and non-diabetic controls. Hypertension was established for 12 weeks by a surgical stenosis of the left renal artery; diabetes mellitus was maintained for 8 weeks by a single intraperitoneal injection of 60 mg/kg streptozotocin. Light microscopic stereology did not reveal significant divergences between diabetic hypertensives and non-diabetic hypertensives. Hypertension induced a focal perivascular and interstitial fibrosis with increased volume densities of non-vascular interstitium and fibrosis (P less than 0.001). Capillary density (QA) was decreased in transverse sections (P less than 0.01) and increased in longitudinal sections (P less than 0.01). This indicates a three-dimensional remodelling of the capillary bed with an increased number of obliquely running capillaries. At least the length density (LV) of capillaries (mm/mm3) tends to be normalized in long-term renovascular hypertension. At the ultrastructural level, a synergism of hypertension and diabetes mellitus was observed: the volume ratio of mitochondria to myofibrils was significantly decreased in hypertensive diabetics, but not in non-diabetic hypertensives or in diabetics. This may enhance the risk of cardiac deterioration. We conclude that the primary target of the synergistic damage in hypertensive diabetic heart muscle disease is the myocardial cell and not the cardiac interstitium.

Animals↗
PubMed1992

Physiological growth of arteries in the rat heart parallels the growth of capillaries, but not of myocytes.

Maladaption to hemodynamic overload, especially to arterial hypertension, has important clinical implications, and it is necessary to obtain criteria in order to discriminate physiological and pathological growth processes. We investigated the physiological growth of intramyocardial arteries in the rat heart. A new stereological method was introduced to determine the length of intramyocardial arteries from counts on histological sections. Four groups of male Sprague-Dawley rats of different ages were investigated. The growth rate of arteries was characterized by the growth coefficient b according to the exponential function y = axb (allometric growth function). Analysis of left ventricular weights (LVW) and total lengths of left ventricular intramyocardial arteries (L) revealed Lv = constant.LVW0.71 (r = 0.77, P < 0.001). The growth coefficient b < 1 indicates that the arterial supply of the heart, i.e. the length density of arteries Lv (length per unit myocardial volume), decreases during normal growth. Empirically, we found L = constant.LVW-0.28 (r = 0.43, P < 0.01). Previously, we estimated growth rates of b = 0.33 for the total length of left ventricular myocytes and b = 0.71 for the total length of capillaries. Thus, growth of intramyocardial arteries considerably exceeds the length increase of myocytes, but is proportional to the length increase of capillaries. Growth analysis of total mitochondrial volume using historical data of our group revealed proportionality to arteries, as well (b = 0.76). This indicates that growth of arteries and capillaries may be determined by oxygen consumption.

Animals↗
PubMed1992

Reduced capillary density in the myocardium of uremic rats--a stereological study.

Using stereological techniques capillaries, interstitium and myocardial fibers were analyzed in perfusion-fixed hearts of subtotally nephrectomized male Sprague-Dawley rats with uremia of 14 months duration (or their sham-operated controls). Uremic rats had higher systolic blood pressure (140 +/- 20.3 mm Hg vs. 119 +/- 6.61 mm Hg) and left ventricular weight/body weight ratio (3.37 +/- 0.09 mg/kg vs. 2.01 +/- 0.12 mg/kg) than controls, and had slight anemia (Hct 35.0 +/- 3.16% vs. 40.4 +/- 3.3%). Length density (Lv) of capillaries, that is, capillary length per unit myocardial volume, was significantly (P < 0.001) decreased in uremia (2485 +/- 264 mm/mm3 vs. 3329 +/- 194 mm/mm3) versus controls. In parallel, surface density and volume density of the capillary lumina were also reduced (7.95 +/- 1.69 cm3/cm3 vs. 11.4 +/- 1.8 cm3/cm3) in the uremic rats. We conclude that in experimental uremia, cardiac hypertrophy is not accompanied by a commensurate increase in capillaries.

Animals↗
PubMed1992

Effects of nifedipine and moxonidine on cardiac structure in spontaneously hypertensive rats. Stereological studies on myocytes, capillaries, arteries, and cardiac interstitium.

Light and electron microscopic stereological studies were performed on the myocardium of spontaneously hypertensive rats (SHR-SP) before and after treatment with nifedipine (27 mg/kg body weight/day) and the antisympathotonic agent moxonidine (8 mg/kg body weight/day). The treated groups were compared with nontreated SHR-SP and normotensive WKY (n = 10 in each group). At the beginning of therapy (when the male SHR-SP were 6 months old), blood pressure was increased and left ventricular hypertrophy had developed whereas pathologic changes of myocardial structure were not observed. After 3 months, the nontreated hypertensive rats showed cardiac fibrosis, activation and proliferation of interstitial cells, wall thickening of intramyocardial arteries, reduced capillarization as well as focal degeneration of myocytes at the ultrastructural level. Both treatments showed similar effects on blood pressure, degree of hypertrophy, and cardiac structure. Blood pressure as well as the degree of hypertrophy were significantly reduced. As far as myocardial fibrosis, capillarization, and regressive changes of myocytes are concerned a complete normalization was observed. Furthermore, nifedipine enhanced capillary supply beyond the normal level by induction of capillary neoformation. Microarteriopathy and activation of nonvascular interstitial cells (first step in development of interstitial myocardial fibrosis) were significantly suppressed by therapy, but the level of the normotensive control could not be maintained. Additional experiments with a low dose combination therapy of nifedipine and moxonidine that did not reduce blood pressure provided evidence that hypertension is an important determinant of the alterations of intramyocardial arteries, but not of cardiac interstitial fibrosis.

Animals↗
PubMed1991

Effects of nifedipine and moxonidine on cardiac structure in spontaneously hypertensive rats (SHR)--stereological studies on myocytes, capillaries, arteries, and cardiac interstitium.

Light and electron microscopic stereological studies were performed on the myocardium of spontaneously hypertensive rats (SHR) before and after treatment with nifedipine (27 mg/kg b.w./day) and the sympatholytic agent moxonidine (8 mg/kg b.w./day). The treated groups were compared with nontreated SHR and normotensive WKY (n = 10 in each group). When the therapy was started in 6-month old male SHR, blood pressure was increased and left ventricular hypertrophy had developed. On the other hand, pathologic changes of myocardial structure were not observed. After 3 months, the nontreated hypertensive rats showed cardiac fibrosis (volume density of fibrosis + 45%), activation and proliferation of interstitial cells (volume density of nonvascular interstitium + 240%), media hypertrophy of small arteries (total volume of arterial media in the left ventricle + 180%), reduced capillarization (length density of capillaries--11%), as well as focal degeneration of myocytes at the ultrastructural level. Both treatments showed similar effects on blood pressure, degree of hypertrophy, and cardiac structure. Blood pressure as well as degree of hypertrophy were significantly reduced (relative left ventricular weights: --25% and --16%). As far as myocardial fibrosis, capillarization, and regressive changes of myocytes are concerned a complete normalization was observed. Microarteriopathy and activation of nonvascular interstitial cells (first step in development of interstitial myocardial fibrosis) were significantly suppressed by therapy (total media volume --40%, volume density of nonvascular interstitium --38%), but the normal level of the normotensive control could not be maintained (+ 70%, + 111% vs WKY). This may be due to the slightly elevated systolic blood pressure despite therapy (+ 25%, vs WKY) or to hormonal factors in SHR which are independent of blood pressure. Since nifedipine and moxonidine are pharmacologically different drugs with different effects on sympathetic activity, one may cautiously conclude that increase in blood pressure itself is an important determinant of arterial, interstitial as well as myocellular alterations which are related to the pathogenesis of hypertensive heart muscle disease.

Animals↗
PubMed1980

Plasma levels of FSH and LH in patients with gonadal dysgenesis during sequential estrogen and progestogen therapy.

We describe the plasma levels of FSH and LH in ten patients with gonadal dysgenesis during treatment with a low dosage sequential estrogen-progestogen preparation. The daily dose of mestranol ranged from 12.5--50 microgram. Norethisterone was administered from day 16 onwards, the dose ranging between 0.75 and 1.5 mg. It was shown that 25 microgram mestranol was effective in lowering the elevated FSH levels significantly (alpha < 0.001). LH levels remained unaffected. The combination of 25 microgram mestranol and 1 mg norethisterone produced an increase of FSH and LH within 12 h, maximum levels being reached within 36 h after which there was a progressive decline. Low doses of estrogen and progestogen appeared capable of evoking physiological hypothalamic and pituitary responses in patients with gonadal dysgenesis. The doses employed were sufficient to induce breast development, growth of sexual hair, and withdrawal bleeding and were probably not high enough to induce rapid bone maturation and consequent stunting of growth.

Adolescent↗
PubMedDate not supplied

Correlates of persisting drug use among former youth multiple drug abuse patients.

This analysis is based on a follow-up study of 48 White male young adults who had been former youth multiple drug abuse patients in day-care treatment. For the most part, these respondents came from middle-class homes. As youthful offenders, many had been sent into treatment as an alternative to incarceration. Approximately six years after terminating their day-care treatments, interview data were collected when most were in their middle twenties. Consistent with previous research, those consuming more drugs were found to be more likely to have resisted treatment, to have trouble with the law, to have poorer work histories and diminished educational attainments, and they showed evidence of poorer psychological health. Surprisingly, the data also indicated that high-volume drug users were more likely to be living in their parental homes, compared to those whose drug use patterns were more moderate. It is suggested that the pattern of taking up residence with one's parents while drug dependent may be encouraged by parental enabling. The implications of these findings for guiding efforts in substance abuse treatment are discussed.

Adult↗
PubMedDate not supplied

Disseminated manifestation of Kaposi's Sarcoma in newly diagnosed AIDS in an african female.

BACKGROUND: Kaposi's sarcomas are the most frequent malignancies in patients with AIDS and there is increasing evidence of an association with human Herpesvirus 8 (HHV-8). A reconstitution of the immune response due to different regimens of highly active antiretroviral therapy (HAART) is the most important step in treatment of Kaposi's sarcomas. Local treatment options include the topic application of alitretionin (9-cis-retinoic acid) as a gel, cryotherapy with liquid nitrogen and intralesional vinblastine, as well as local laser or low-dose X-ray treatment. A systemic chemotherapy can be taken under consideration in selected cases with clinical significant visceral lesions or aggressive sarcomatous behavior with anthracyclines, taxanes, as well as an immunomodulatory treatment with alpha Interferon. CASE REPORT: The case of an african emigrant is described. Hospitalized due to recurrent fever and diarrhea, the diagnosis of AIDS was quickly established. The physical examination revealed multiple nodular, painless skin lesions suspicious of Kaposi's sarcoma. The diagnosis was confirmed histologically, later on also in bronchial and duodenal biopsies due to the atypical subepithelial vessels with slit-like appearance and prominent endothelia. CONCLUSIONS: Cutaneous lesions in patients with dark skin colour may be unfamiliar to European physicians. In patients with HIV-infection, nodular skin lesions should lead suspicion to Kaposi's sarcoma. If this diagnosis is established, it should be clarified, if other locations (e.g.: intestine, respiratory tract) are involved, too.

AIDS Serodiagnosis↗
PubMedDate not supplied

[Neoangiogenesis: from molecular biology to clinical medicine].

Cardiovascular disease is the most common cause of premature death in patients with end-stage renal disease, probably due to a specific "uraemic cardiomyopathy" This article reviews the pathogenesis of cardiac changes in uraemia and particularly the role of an impaired vessel formation. Experimental and autoptic data showed remarkable changes in heart capillarization in renal failure, i.e. a decrease in myocardial capillary supply and a concomitant increase in intercapillary distance. Promoting the formation of new collateral vessels in ischemic tissues using angiogenic growth factors (therapeutic angiogenesis), such as VEGF, constitutes a promising approach for the treatment of uraemic cardiomyopathy.

Humans↗